Generally, thermal imaging cameras using far-infrared (FIR) light do not sense a visible light area but sense a far-infrared area. That is, the thermal imaging cameras senses infrared thermal energy that is produced by a subject, and obtains the sensed result as a thermal image. Due to this characteristic, the thermal imaging cameras may be used to sense a person having a body temperature.
Recently, a pedestrian detection apparatus using an FIR camera is applied to vehicles. The FIR camera applied to a vehicle needs to provide consistent detection performance irrespective of a current driving environment of the vehicle. That is, the FIR camera applied to a vehicle needs to provide consistent detection performance even in an urban area in which scattered reflection due to ambient light sources is severe or an out-of-town area in which scattered reflection due to ambient light sources is not severe.
Therefore, a function of adjusting detection sensitivity is fundamentally added to a related art FIR camera applied to a vehicle, for providing consistent detection performance. The sensitivity adjustment function adjusts the setting of a radiant temperature difference between objects for a captured thermal image, thereby adjusting detection sensitivity.
However, there is a limitation in adjusting detection sensitivity in an urban area in which the scattered reflection of light emitted from an ambient building, the scattered reflection of light emitted from a signboard attached to an ambient building, and particularly, the scattered reflection of light of front and rear vehicles are severe. Furthermore, FIR cameras are expensive equipment, but, as described above, the FIR cameras cannot satisfy detection performance for price which a user desires, in an urban area in which scattered reflection is severe.
Moreover, it is possible to detect a pedestrian using a complementary metal-oxide-silicon (CMOS) camera relatively cheaper than FIR cameras. However, CMOS cameras do not obtain an image of a subject but sense infrared thermal energy produced by the subject, and thus do not have a sensitivity adjustment function using the radiant temperature difference of a subject. That is, in an urban area in which scattered reflection is severe, it is especially unable to detect a night pedestrian, and, as in FIR cameras, it is difficult to clearly determine if an object is a pedestrian or an animal.